1. Technical Field
The present invention relates to a lens driving apparatus that drives a lens-barrel body to both sides in the light axis direction of a lens, and an optical pickup unit disposed with this lens driving apparatus on a light path between a laser light source and an objective lens.
2. Description of the Related Art
With regard to a signal recording medium such as an optical disk used to optically reproduce or record signals with the use of laser light, the Blu-ray standard and the HD-DVD (High Density Digital Versatile Disk) standard are proposed which are new optical disk standards achieving recording densities higher than prevailing optical disk standards, i.e., DVD or CD.
An optical pickup unit corresponding to the optical disk standards achieving higher recording densities requires precise optical characteristics in association with the improved recording densities so as to enhance signal recording quality, and an optical pickup unit is known that is disposed with an aberration correction lens correcting spherical aberration generated by a light emitting optical system guiding laser light to a disk (see Japanese Patent Application Laid-Optical Publication No. 2003-257069).
The aberration correction lens includes a beam expander and a collimator lens, and spherical aberration is corrected in a condensed spot of the laser light which is irradiated to a signal layer through a cover layer (transparent substrate) covering the signal layer of the disk by allowing the aberration correction lens to be driven in the light axis direction to displace the aberration correction lens in the light axis direction.
By the way, in a lens driving apparatus that drives the lens in the light axis direction, a piezoelectric element is used as a driving source, and in a known technology, one end of the piezoelectric element is used as a fixed end; a driving bar is fixed to the other end of the piezoelectric element; a lens-barrel incorporation a lens is supported by the driving bar such that the lens-barrel can be slid and displaced relative to the driving bar; and the lens-barrel is driven in the light axis direction of a predetermined lens by expanding and contracting the piezoelectric element and by controlling the expanding and contracting speed of the piezoelectric element (see Japanese Published Patent No. 2633066).
By enabling the driving of the aberration correction lens with the use of such a lens driving apparatus, an optical pickup unit capable of correcting spherical aberration is provided.
By the way, the above lens driving apparatus includes a large number of components partially because a driving bar and a guide shaft are used to support the lens-barrel, and is is advantageous in miniaturization.
If a lens-barrel is slid by the driving bar and the guide shaft passing through the lens-barrel, the apparatus becomes susceptible to dust and normal movement may be disturbed, and also clearance is needed around the driving bar and the guide shaft to allow the sliding motion. However, when the lens-barrel is moved due to the clearance, the lens-barrel may tilt or misalignment of the light axis may be generated, resulting in a tilt of the lens or decentering of the lens, which is problematic.